1. Field of the Invention
The present invention relates to a novel .alpha.-glycosyl hesperidin, sometimes hereinafter referred to as .alpha.-glucosyl hesperidin, and its preparation and uses.
More particularly, the present invention relates to .alpha.-glycosyl hesperidin wherein equimolar or more D-glucose residues are bound to hesperidin via the .alpha.-bond.
The present invention also relates to a process to prepare .alpha.-glucosyl hesperidin, which comprises allowing a saccharide-transferring enzyme to act on a liquid containing hesperidin together with an .alpha.-glucosyl saccharide to form .alpha.-glucosyl hesperidin, and recovering the .alpha.-glucosyl hesperidin.
The present invention further relates to foodstuffs including beverages and processed foods, pharmaceuticals for susceptive diseases including preventive and remedy therefor, and cosmetics including skin-refining agent-and skin-whitening agent, characterized in that they all contain the .alpha.-glucosyl hesperidin obtainable by the process.
2. Description of the Prior Art
Hesperidin, whose chemical structure is given below, has been known as a yellow pigment and vitamin P with physiological activities such as stabilization of blood vessel, prevention of hemorrhage and regulation of blood pressure, and used from ancient times in foodstuffs, pharmaceuticals and cosmetics. ##STR1##
It is known that vitamin P takes part in some physiological activities of vitamin C in vivo; for example, in the hydroxylation of proline and lysine which are necessary to synthesize collagen as the main element of living connective tissues; the oxidation-reduction reaction of cytochrome C wherein Fe.sup.+++ is reduced into Fe.sup.++ ; and in the immunopotentiation via the increase of leukocyte. These are because vitamin P plays a significant role in the maintenance and promotion of health in living bodies.
Nowadays the use of hesperidin is not limited to agents which enrich vitamin P as a nutritive element, but is extending in various applications. More particularly, because of the chemical structure and physiological activities, hesperidin is useful as a yellow coloring agent and antioxidant alone or in combination with one or more vitamins, for example, in foods, beverages and pharmaceuticals for susceptive diseases such as preventive and remedy for circulatory diseases, as well as a yellow coloring agent and uv-absorbent in cosmetics such as skin-refining, melanin-formation inhibitory agent and skin-whitening agents.
Hesperidin is, however, hardly soluble in water (only about 1 g in 50 liters of water or about 0.002 w/v % at ambient temperature). This renders its practical use very difficult.
To improve this low water-solubility, a method wherein dimethyl sulfuric acid is allowed to act on hesperidin to convert it into its methyl derivative having an increased water-solubility has been proposed.
The method is, however, unsatisfactory in view of toxicity, safeness and economical efficiency because it is carried out by an organic chemical procedure using a harmful dimethyl sulfuric acid which renders the purification of the resultant derivative very difficult. Another drawback is that the methyl derivative has a bitter taste.